Optical sources are in widespread use for data storage and communication applications, and include lasers of many different types and configurations. By way of example, such lasers may be implemented using one or more laser diodes each having an associated laser driver circuit.
Lasers are utilized in a wide variety of optical disk recording and playback systems. Standardized optical disk storage formats have recently evolved from Digital Versatile Disk (DVD) to Blu-ray. A Blu-ray disk is read using a blue laser having a wavelength of 405 nanometers, significantly shorter than the 650 nanometer red laser used to read DVDs. Information can therefore be stored at a much higher density on Blu-ray disks. For example, a single layer Blu-ray disk can store about 25 Gigabytes (GB) of data, compared to about 5 GB for a DVD. Higher storage densities can be achieved by configuring the optical disk to include multiple storage layers, as is well known.
In addition, three-dimensional (3D) image information for movies or other types of content can be stored on Blu-ray disks and other optical disks. A 3D optical disk playback device can read such information from the optical disk and provide a corresponding 3D image signal output for presentation on a television or other display device, thereby providing a 3D viewing experience to its users.
Lasers are also commonly utilized in other types of recording applications, including magnetic recording systems. For example, a magnetic recording technique known as heat-assisted magnetic recording (HAMR) utilizes a laser to locally preheat an area on the surface of a magnetic storage disk prior to performing magnetic recording in that area. This facilitates the magnetic recording process, thereby allowing data to be stored in a higher density than would otherwise be possible.
There are numerous other types of systems that utilize lasers outside of the recording or playback context, including optical communication systems. In such communication systems, for example, lasers may be used to generate modulated optical signals for transmission over optical fiber.
In systems of the type described above, a laser driver circuit may be utilized to drive current to a laser diode in order to allow the laser diode to turn on so as to provide light output. The laser diode typically needs to be transitioned rapidly between its on and off states in order to support the high data rates often utilized for recording, playback or communication applications. The driver circuit is coupled to the laser diode via one or more transmission lines. It is particularly important at high data rates that these transmission lines coupling the driver circuit to the laser diode be terminated in an appropriate manner, so as to reduce any signal loss or other degradations that may be induced by reflections or standing waves resulting from impedance mismatch.